The instant invention relates to an apparatus for handling elongate members, e.g., drill pipe, drill collars, well tubing, etc., at a well drilling site. More particularly, this invention provides a cable transport mechanism which may be used either to deliver pipe to the elevated rig floor well derrick or to lay down pipe from the rig floor to a lower storage area. Hence, the apparatus herein may be employed throughout the drilling operation for pipe handling tasks, but will be especially useful in pipe lay down operations.
At the well site where an oil well is being drilled or reworked, it is necessary that provision be made for handling of the drill pipe, well tubing, well casing, or drill collars which are used in the well. For example, during the drilling operation, it is continually necessary to provide additional lengths of drill pipe or the like to the derrick as the drilling progresses. Similarly, when the drilling operation is concluded or when problems are encountered during drilling, it may be necessary or desirable to remove the drilling string from the borehole. Accordingly, the operators at the well site are constantly confronted with the problem of efficiently handling the various tubular members used during the drilling operation, and of transporting these tubular members between the rig floor and a nearby storage area where the collars and drill pipe are typically maintained on racks in a stand-by position.
It has been customary in handling pipe or other tubular goods at a well site to provide an inclined trough or skidway adjacent the open side of the derrick to facilitate the transfer of the pipe from the drilling rig substructure, called the rig floor, and the pipe rack storage area. However, due to the weight of these tubular members, such relatively uncontrolled handling can result in damage to thread connections, and also because of the inordinate amount of manual handling which is required, can result in injury to workers at the well site.
Considerable attention has been directed toward devising various types of drill pipe handling apparatus in order to facilitate transfer of tubular goods from the pipe storage area to the usually elevated rig floor of the derrick substructure, and subsequently to transfer the same back to the storage area. One approach has been to provide a mechanical device with a pipe holding through which will accept a length of pipe from the storage area and thereafter lift the pipe or incline it in order to "feed" the pipe upwardly toward the rig floor. Illustrative of such devices is U.S. Pat. No. 3,559,821. Alternatively, powered trolleys riding on tracks could be provided to transport the pipe from the rig floor to the storage area or vice versa, as shown in U.S. Pat. No. 3,268,095 and the like.
Another approach has been to use a cable transport system to handle the pipe. A cable system has inherent advantages in that it can be most easily adapted to the conditions at the well site. Unlike purely mechanical systems, cable systems can usually be adapted to deliver pipe from a convenient storage area, which may be in a different position at different well sites to the rig floor, which may vary in elevation depending upon the particular well being drilled. U.S. Pat. Nos. 3,532,229 and 3,368,699 disclose cable systems for handling pipe at a well site. But in these patents, the pipe is secured only at one end to the cable system, and hence, manual attention of the workers is required to prevent damage to the free end of the pipe. Moreover, the systems disclosed in these patents rely to significant extent upon the use of the traditional pipe skidway.
Another approach has been to use transport carriages supported on a cable to handle the pipe. The use of front and rear carriages to support the pipe at the ends remedies the problems associated with a free and unsupported lower end as found in the above-described prior cable systems, but a system of this type does not permit rapid pickup or laydown operation. Also, if a change is made in the size of pipe to be handled, the carriages must be changed to accommodate the new pipe. An example of this approach to pipe handling at a well site is the apparatus disclosed in U.S. Pat. No. 3,825,129.